Device for the central feeding of tanks such as circular grit traps, grit classifiers or settling tanks of circular construction

ABSTRACT

A device for centrically charging tanks (9) with a spin chamber (1, 10) connected to an inlet (20) and to a vertical downpipe (2, 12) ending seamlessly in a trumpet-shaped mouth (3, 18). Rotary flow charges circular settlement tanks and sand sorters and sedimentation tanks in such a way that the Coanda effect is activated at the trumpet-shaped mouth (3, 18) and in turn causes the rotary outflow of fluid from the vertical pipe (2, 12) to be diverted into the horizontal plane or vertically upwards as well as a radially symmetrical flow in the tank (9). There is a guiding pipe (14, 16) in the downpipe (2, 12) with preferably circular apertures around its periphery and which is open to the atmosphere at the top.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a device for the central feeding of tanks suchas circular grit traps, grit classifiers or settling tanks of circularconstruction.

The subject of the invention is also a process for feeding such circulargrit traps and grit classifiers and settling tanks of circularconstruction. Finally, the subject of the invention is also the use ofthe process and of the device for feeding circular grit traps and gritclassifiers and settling tanks of round construction in sewage treatmentplants.

2. Description of the Prior Art

For reasons of operational reliability, it is usually necessary, in thecase of many waste-water and sludge treatment units of the sewagetreatment plant, to separate the grits and other mineral substances,which have been entrained in the waste water, from the putrescible,organic substances. The conventional devices for degritting the wastewater are, depending on construction type and operation, designated asdeep, shallow, circular and aerated grit traps. In the case of theprior-art circular grit traps and grit classifiers of circularconstruction, the waste water is fed tangentially to a circularhopper-bottomed tank. After flowing through a centering angle of over180°, the waste water passes into the outflow. The great disadvantagewith conventional circular grit traps and grit classifiers of circularconstruction, however, is that, owing to the tangential introduction,the tank volume (region through which flow occurs effectively) providedis not utilized to the optimum degree and the hydraulic efficiencythereof is thus only approximately 50%.

The operating principle of conventional circular grit traps is based onthe fact that, in curves, the bed load moves inside the curve. Theforced circular motion causes, owing to the centrifugal force in thecircular grit trap, a rise in the water level from the rotational axisoutwards. Under the influence of the superatmospheric pressure in theedge zone, a circular motion, which is directed towards the center atthe bottom, is thus superimposed in the throughflow. This results in ahelical flow through the tank. Owing to the radial transverse flow,which is particularly strong at the bottom as a result of the reducedtangential velocity of the waste water there, the grit which has sunk tothe bottom is conveyed into the hopper-shaped collecting chamber, in theaxis of which there is arranged at least one cylindrical pump pit withmammoth pumps.

SUMMARY OF THE INVENTION

The object of the invention is to provide a device with a centralfeeding of such circular grit traps and grit classifiers and settlingtanks of round construction which is of simplified design, such that,with the same inflow quantity and the same settling volume, an increasein the hydraulic efficiency from 50% to 90% is achieved.

It is further the object of the invention to specify such a process forcentral feeding, in which the efficiency is improved.

This is achieved in the case of a device for the central feeding of suchtanks having a swirl chamber which is connected to the inflow and is inconnection with a vertical gravity outlet pipe, a trumpet-shaped bodywidening from a transition region adjoining the gravity outlet pipe in aseamless manner, in that rotary flow having angular momentum is utilizedfor feeding circular grit tanks and grit classifiers and settling tankssuch that there is activated, at the trumpet-shaped body widening fromthe transition region, the Coanda effect which, for its part, causes adeflection of the liquid stream, emerging from the vertical pipe andhaving angular momentum, at least in the horizontal direction orvertically upwards and also causes a radially symmetrical drain-off inthe tank, and in that there is arranged, in particular, a conduit pipe,centrally in the gravity outlet pipe, which has preferably circularopenings over its circumference and is open at the top towards theatmosphere.

By trumpet-shaped body or widening, it is understood by those ofordinary skill, particularly in view of the drawing figures that thebell shaped body to which is attached the vertical pipe is somewhatsimilar in appearance and geometry to the bell end of a horn such as forexample a trumpet. The surface geometry of this bell shaped ortrumpet-shaped body or widening, is such that angles (β) formed bytangent lines to the inner facing surface of the bell and the horizontalwill go successively from about 90 degrees to about 0 degrees. Thetangent lines, starting at a transition region, that is the region wherethe tangent lines would be changing from substantially vertical towardhorizontal in a smooth manner and moving toward a detachment edge of thebell. Thus the angles formed by such tangent lines basically andsuccessively go from axially directed to radially directed moving fromthe transition region to the detachment edge.

It is not denied that processes are known per se which cause aseparation of the mineral constituents from the waste water by utilizingthe force of gravity and centrifugal force. In these, however, feedingis not carried out centrally from the top with the simultaneousutilization of a swirl motion and the so-called Coanda effect.

It is known that the hydraulic efficiency of circular grit traps andgrit classifiers and settling tanks of circular construction is coupledwith the region through which flow occurs effectively and the averageflow velocities. Instead of the desired 80%, only a hydraulic efficiencyof 50% could thus be achieved, in practice, with the conventionalstructures. From this point of view, the measure taken by the inventionsignifies a considerable step forwards.

Furthermore, it is generally known that rotational symmetry cannot bepresupposed during flow through the tank since a tangential incomingflow does not stabilize the vortex axis to a sufficient extent. In theactual flow area, the flow center is thus twisted helically and theseparating surface is unstable.

The advantages achieved by the invention consist, in particular, in thatthe rotational symmetry is better utilized by the central feeding fromthe top. A further advantage is that, after leaving the vertical pipe atthe edge of the trumpet-shaped or toroidal body, the liquid phase havingangular momentum is deflected and guided by utilizing the Coanda effectand can thus be precisely anticipated. At the same time, in addition tothe force of gravity, a centrifugal force acts on the mineralconstituents, entrained in the liquid phase, owing to the deflection onthe toroidal body i.e., the trumpet-shaped body. When the liquid phaseis deflected, the grit particles are thus forcibly flung out of saidphase and immediately sink in the direction of the base. It is also ofgreat import that the liquid stream, has angular momentum, produced bythe swirl chamber.

Expediently, we the swirl utilized [sic] such that swirl effect andCoanda effect are intensified synergistically. "Coanda effect" means thedeflection of a jet towards a curved wall. The jet is deflected from itsoriginal direction and will attach itself to neighboring body surfacesand also follow any sharp changes in direction without separation. Theattachment is based on a subatmospheric-pressure effect in the region ofthe wall-side jet edge. By Coanda effect, according to the definition,the following is understood: the characteristic or capability offree-fluid-flows having small cross-sections to lay itself or applyitself to vicinal body surfaces and also to follow severe alterations ofdirections of the surface structure without any peeling off (i.e.,without separating from that surface).

An exteriorly similar design has been disclosed by German PatentSpecification 159738. In this case, inflow does take place into agravity outlet pipe likewise via a swirl chamber, the motion isconverted into a rotating motion, but the rotational motion according toGerman Patent Specification 159738 serves to trigger centrifugal forcesin the gravity outlet pipe in order that the heavier particles aredeposited outwardly. The design comprises a gravity outlet pipe which isimmersed in a separating tank and has lateral openings above the mouth(nozzle), and the nozzle part is arched in a bell-like manner, theopenings thus being taken sideways as compulsory channels. Afterreaching the top lateral annular opening, the heavier particles betweenthe gravity outlet pipe, widened in the form of a nozzle, are thenscattered into the separating tank in the horizontal direction, whereasthe lighter particles pass, for scattering out, through the interior ofthe nozzle beneath the heaviest particles. The heavy particlesostensibly serve as a filter for the lighter particles. The nozzle thusforcibly deflects the liquid jet.

This is not the case with the device according to the invention, inwhich, once at the edge of the trumpet-shaped body, the Coanda effect isforced to take place and, in addition to the force of gravity, acentrifugal force acts on the constituents, entrained in the liquidphase, owing to the deflection. When the liquid phase is deflected, thegrain particles are thus forcibly flung out of said phase andimmediately sink. Moreover, in the case of the present invention,special bodies such as separate nozzle bodies or the like are dispensedwith.

It is, on the other hand, not denied that utilization of the Coandaeffect within the specialist field is already known, albeit in adifferent step of the purifying process and for a different purpose.Applicants' own U.S. Pat. No. 5,422,017, issued Jun. 6, 1995 is basedupon DE GM 9112947 German Patent No. 41 34 388 and defines and describesthe use of the so-called Coanda tulip for central charging of circulartanks with sewage water. A centrally inserted horizontal circularcontrol disc in the region of the transition from the verical pipe to asmoothly continuously adjoining bell shaped component.

Of course, there are also considerable advantages according to theinvention if a conduit pipe is not used.

If use is made of such a central conduit pipe, which passes from the topside of the swirl chamber to just above the water level in the gravityoutlet pipe (tank water level), then the vortex axis can additionally bestabilized successfully. If, in addition, the conduit pipe is providedwith holes of corresponding size distributed-uniformly over thecircumferential surface, then the size of the air bubbles and of the airsupply can be influenced. In combination, the conduit pipe centrallypositioned within the vertical gravity pipe creates an annular gap atthe input (small diameter end) end--the transition region. The fluidemerging from this annular gap "hugs" the inner surface of thetrumpet-shaped body (widening)thus being deflected from vertical towardsthe horizontal. This combination of the vertical pipe and the conduitpipe therewithin, while not essential to the creating of the Coandaeffect, enhances the performance because the fluid is caused to beproximate the inner curving wall of the bell-shaped or trumpet-shapedbody.

In a development of the invention, the vortex axis can be stabilized ifthe conduit pipe is designed in a manner corresponding to the form of avortex sink.

If an upstream immersed baffle is additionally fitted at a defineddistance from the tank edge, then floating substances and greases mayadvantageously be retained. Owing to the circular motion of the tankflow, the floating substances and greases can be discharged at a certainpoint by adeptly fitting an inner immersed baffle additionally runninghelically in the direction of the center.

A further configuration of the invention consists in taking the upstreamimmersed baffle until it reaches as far as the tank cover and connectingit rigidly thereto. When the separator is full, an air cushion in whichthe floating substances and greases circulate consequently forms withinthe upstream immersed baffle, beneath the tank cover. The undersidealways remains dry, and unpleasant, aggravating odors owing toputrefying grease are thus avoided.

The subject of the invention is also a process for the central feedingof circular grit traps, in which a swirl is produced in order toactivate the so-called Coanda effect, and the Coanda effect is utilizedsuch that it serves, for its part, for separation of the mineralconstituents entrained in the liquid phase and for the decelerated anduniform introduction, having angular momentum, into the circular tank,and the [sic] an air intake is provided in the center of the vortex corearising as a result of the tangential introduction.

The swirl is preferably utilized such that swirl effect and Coandaeffect are intensified synergistically.

Use can be made of such a device or such a process for clarifying wastewater, in general for liquid/liquid separation, the separation of solidsand liquids, for example as grease trap, or for the separation ofshredded refuse and sewage, or as petrol separator. Usually, the deviceaccording to the invention, in the first-described embodiments, isutilized for separation of the mineral constituents entrained in theliquid phase and for the decelerated and uniform introduction, havingangular momentum, into the circular tank.

In contrast, the arrangement of an aerating system has often beennecessary up until now in order that the organic constituents in thewater did not settle in the circular grit trap, but this involved highcosts.

By preferably fitting an air-supply opening on the top side of the swirlchamber according to the invention, on the other hand, an air compressorcan be dispensed with, since, in this region, air passes into the liquidflow as a result of subatmospheric pressure. Conventional tanks having acapacity of 4.5 m³ were no more efficient than the special circular tankaccording to the invention, having a capacity of 0.9 m³. The efficiencywas the same in both cases. The particle sizes of less than 0.2 mm whichcan only be achieved with difficulty with known devices compare with theparticle sizes of 0.125 mm which can readily be achieved according tothe invention. The devices (P 4134388.3) defined in Applicants' own U.S.Pat. No. 5,422,017, for feeding circular tanks by waste water operatedwith an inserted, horizontal, circular plate cam which can now betotally dispensed with.

The abovementioned upstream immersed separating baffle at a defineddistance from the tank edge gives rise to a particularly favorableseparation in the case of an open top gravity discharge.

If the upstream immersed baffle reaches as far as the tank cover and isconnected rigidly and in a sealed manner thereto, then, when theseparator is full, an air cushion in which the floating substances andgreases circulate consequently forms within the upstream immersed bafflebeneath the tank cover.

In a development of the invention, the tank wall as such can be taken asfar as the cover, as a result of which the necessity for a separateupstream immersed baffle is eliminated. Peripheral slots in the tankwall permit a pressure discharge of the liquid to a pipe which encirclesthe tank and is connected to the slots.

The space exhibiting floating substances and containing air in anincreased state of compression and located above the liquid level can beemptied via a discharge pipe which opens discontinuously. If the pipe issuddenly opened approximately every hour, then the contents (the gas orthe air and the sludge deposited in the floating layer) shoots outwardsthrough the pipe. Pumps or the like are not necessary, which signifies afurther great advantage of the invention.

The invention with or without conduit pipe can be used for tanks of theabovementioned type for liquid/liquid separation, the separation ofsolids and liquids, for example as grease trap, or the separation ofshredded refuse and sewage, or as petrol separator. The diameter of theopenings of the conduit pipe can, at most, be equal to d/2 (conduitpipe). The regulation of the air supply to the conduit pipe can takeplace via a ballcock, throttle valve, which may also be self-regulating,or any suitable member.

By way of example, embodiments of the invention are now to beillustrated in more detail with reference to the accompanying drawings,in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of a first embodiment, which servespredominantly as grit classifier;

FIG. 2 shows a plan view of FIG. 1;

FIG. 3 shows a variant of the embodiment shown in FIG. 1, with thearrangement of a conduit pipe;

FIG. 4 shows a variant of FIG. 3, with a differently configured conduitpipe;

FIG. 5 shows an embodiment with immersed baffle;

FIG. 6 shows a plan view of FIG. 5;

FIG. 7 shows a variant, in particular for liquids charged with floatinggrease and other constituents; and

FIG. 8 shows a simplified variant of FIG. 7.

DETAILED DESCRIPTION OF THE INVENTION

The embodiment represented in FIGS. 1 and 2 shows a circular tank 9 withcentral feeding. A horizontal inflow is connected, in a transition-freemanner, to a swirl chamber 1. Onto the swirl chamber 1 there is attacheda vertical pipe 2 which merges, in a transition-free manner, into atrumpet-shaped widening 3 (both in the vertical axis of the overalldiagram). A classifying worm 6 known per se is located at the bottom ofthe circular tank 9, at a hopper-like constriction. The circular tank isprovided with a discharge 8. The helical configuration of the inflow isshown clearly in FIG. 2.

According to the invention, the waste water flows horizontally to theswirl chamber 1. In the swirl chamber, the liquid stream is subjected toswirling, whereupon it flows through the vertical pipe 2 in helicalmotion. At the end of the vertical pipe 2, the swirl intensifies theflow through the trumpet-shaped arching and thus intensifies,synergistically, the attachment of the jet to the trumpet-shaped innercurve and thus the deflection downwards, in a radial direction and evenupwards. Deflection angle β characterizes or represents the angle of thetangent line to the inner surface of the bell shaped body ortrumpet-shaped widening. Clearly this angle could be of different valuedepending upon application. An obvious method of varying the deflectionangle β would be to make the bell shaped body replaceable by providingfor the removeable attachment of the bell shaped body to the output endof the vertical pipe, i.e., at the region of transition. The bell shapedbody would connect to a mateable edge providing for a smooth andcontinuous transition from vertical to almost horizontal. There may beprovided a variety of bell shaped bodies, i.e., trumpet-like bodies,each of which would have a different geometry such that the deflectionangle β is thereby different. The flow at the edge of the trumpet-likebody may thus be directed from nearly vertical to substantiallyhorizontal. Finally, the liquid jet having angular momentum flows, afterdeflection, into the circular tank.

A grit classifier of this type can operate with a circular tank of, forexample, 1.5 m in diameter, with a height of not more than 1.6 mdiameter [sic] and a circular-tank capacity of 1.5 m³.

The entire tank is thus activated by:

centrifugal force, caused by the swirl chamber, acting on the wastewater and producing a helical motion,

centrifugal force, owing to deflection at the Coanda trumpet (particlesare flung out), and

centrifugal force owing to a rotary flow, having angular momentum, inthe tank.

According to FIG. 3, flow takes place into a swirl chamber 10. From theswirl chamber 10, liquid passes into a gravity outlet pipe 12 which hasa trumpet-shaped widening 18.

Reaching into the gravity outlet pipe there is provided a conduit pipe14, to be precise centrally in the gravity outlet pipe. The conduit pipeis open at the top, but has an air regulating system. Over itscircumference, the conduit pipe bears openings which can be adapted torequirements. Air is conveyed, in the form of bubbles, from the passingliquid stream into the circular tank since a vortex core inevitablyoccurs in the axis of the gravity outlet pipe, said vortex coreotherwise circulating eccentrically. With increasing centrifugalacceleration, more openings are released. It can be seen clearly how theliquid stream is attached to the Coanda Tulip and, when the liquid phaseis deflected, the grit particles are thus forcibly flung out of saidphase and immediately sink.

FIG. 4 shows an embodiment similar to FIG. 3. Here, too, a conduit pipe16 is provided in the gravity outlet pipe 12 and is again provided withopenings over the circumference, but it is designed in the manner of avortex sink, i.e. at the top it has a large trumpet opening whichcontinues downwards into the gravity outlet pipe into the pipe [sic].

FIGS. 5 and 6 show another embodiment which is particularly suitable forgrease separation or the separation of other particles which arefloating due to the addition of air or flocculating agents. The heightof the immersed baffle 24 is, for example, 15 cm, it being positionedsuch that 3 cm are immersed in the tank water level and, for example, 12cm project out (a third is immersed and three quarters project out[sic]). The entire free surface within the immersed baffle 24 thusserves as a trap for floating substances and solids. Reference numberswhich are the same as in the other figures denote the same objects. Itcan be seen how the floating substances accumulate within the upstreamimmersed baffle 24, and the open top gravity discharge, at a defineddistance, can be seen at 22. This embodiment operates without a conduitpipe.

In the plan view of FIG. 5 shown in FIG. 6, a further supplement to thetrap for floating substances and greases is provided. An inner immersedbaffle 30 running helically in the direction of the center leads awayfrom the upstream immersed baffle 24. The height of the inner immersedbaffle is the same as the height of the first-mentioned upstreamimmersed baffle and is, for example, likewise 15 cm. The discharge isspecified at 28 and the tank edge at 26. The sludge particles will thusmove towards the center and be conveyed upwards in suspension. The airbubbling out of the mixture causes the formation above the liquid level,at 28, of the floating cover, comprising grease constituents, and,thereabove, a main chamber which keeps the cover of the tank dry inside.

FIG. 7 shows a further embodiment. Here, an upstream immersed baffle 43in the tank 26 is taken, in the same way as the inner immersed baffle,as far as the tank cover 44 and is welded thereto. This results in theformation, beneath the tank cover, of an air cushion in which thefloating substances and greases 44' circulate. At 40, the air isincreasingly compressed; the open top gravity discharge 44" can again beseen at 42. The Coanda trumpet 3 and the swirl chamber 10 are the sameas in the preceding embodiments, and the inflow is specified at 20. Viathe pipe 42 provided with shut-off means, sludge/floating substances 44'together with air can be discontinuously discharged or ejected or flungout owing to the superatmospheric pressure. This can take place, forexample, every hour.

FIG. 8 shows a further embodiment, which is simplified with respect toFIG. 7. The tank wall 50 is simply taken as far as the cover and weldedto said cover 44. The inflow 20, swirl chamber 10 and the Coanda trumpet3 are unchanged. Floating greases collect at 44', an air cushion beginsto form under increasing pressure at 40 and discharge again takes placevia the pipe 42 for discharging floating substances and greases 28. Theliquid discharge takes place via slots 48 which run into a pressuredischarge line. This is configured as a pipe encircling the tank 50. Adischarge under pressure thus takes place, i.e. this is actually aclosed system. It can be seen that no pumps are used. The outer immersedbaffle is dispensed with in this example. Only the inner immersed baffleis present, if we may put it this way.

The measure according to the invention can thus be carried out

a) without a conduit pipe (see the abovementioned advantages, inparticular for the first embodiments)

b) with a closed conduit pipe. In this case, the conduit pipe is used,in particular, to stabilize the vortex core which spirals around theconduit pipe. This embodiment was not particularly shown in thedrawings, and

c) with a conduit pipe, which is open at the top and bottom and isprovided with holes over the circumference, as a variant the holesincreasing in diameter to correspond to the flow conditions.

As in a further configuration of the measure according to the invention,the supply of air can also take place via a compulsory feed means. Thecompulsory feed means can, for example, be a compressor. Consequently,the special effects of the addition of air can be achieved.

Flocculating agents may preferably also be added from the top to the airintake, if the operator of the plant deems this to be necessary. Ifappropriate, flocculating agents may also be added to the compulsoryfeed means.

We claim:
 1. A device for central feeding of a tank with fluid byutilization of the Coanda effect, comprising:a vertical gravity outletpipe oriented substantially vertically with respect to gravity, with afirst end and a second end, said second end directed into a centralportion of said tank; a swirl chamber, said swirl chamber in flowcommunication, at an input end thereof, with input flow of said fluidand attached in flow communication, at an output end thereof, with saidfirst end of said vertical gravity outlet pipe wherein fluid supplied tosaid swirl chamber is caused to move in a helical flow as it passesthrough said vertical gravity outlet pipe from said first end towardsaid second end of said vertical gravity outlet pipe; a bell shapedbody, trumpet-shaped in that said bell shaped body is configuredsimilarly to a bell end of a trumpet and having a small diameter end anda fluid detachment end, said small diameter end connected to andadjoining said second end of said vertical gravity outlet pipe definingthereby a smooth and continuous region of transition from said secondend of said vertical gravity outlet pipe to said small diameter end ofsaid bell shaped body; and said vertical gravity outlet pipe and saidbell shaped body cooperating in such a manner that said fluid emergesfrom said fluid detachment end of said bell shaped body in a directionsubstantially radial relative to said vertical gravity outlet pipe, saiddirection of said emerging fluid being a result of said Coanda effectand into said tank wherein said fluid is caused to radiallysymmetrically drain-off from said tank.
 2. The device for centralfeeding of a tank with fluid by utilization of the Coanda effect,according to claim 1, wherein said bell shaped body widens in a mannersuch that axially directed tangent lines to a fluid contacting surfaceof said bell shaped body smoothly change from a substantially verticalwith respect to gravity direction at said region of transition toward asubstantially radial direction relative to said vertical gravity outletpipe substantially at about said fluid detachment end of said bellshaped body.
 3. The device for central feeding of a tank with fluid byutilization of the Coanda effect, according to claim 2, furthercomprising:a conduit pipe centrally disposed in said vertical gravityoutlet pipe, said conduit pipe having one open end open to atmosphereand another open end disposed substantially at said region oftransition, said conduit pipe wall having a plurality of aperturestherethrough, said conduit pipe providing thereby a supply of air tosaid vertical gravity outlet pipe; and said conduit second end openingand a fluid contact surface of said vertical gravity outlet pipedefining an annular gap in said region of transition, said annular gapand said bell shaped body cooperating in such a manner that said fluidemerges from said fluid detachment end of said bell shaped body in adirection substantially radial relative to said vertical gravity outletpipe, said direction of said emerging fluid being a result of saidCoanda effect and into said tank wherein said fluid is caused toradially symmetrically drain-off from said tank.
 4. The device forcentral feeding of a tank with fluid by utilization of the Coandaeffect, according to claim 3, further comprising means for regulation ofsaid supply of air into said conduit pipe into said vertical gravityoutlet pipe through said plurality of apertures.
 5. The device forcentral feeding of a tank with fluid by utilization of the Coandaeffect, according to claim 3, further comprising means for compulsoryfeeding of said supply of air into said conduit pipe into said verticalgravity outlet pipe through said plurality of apertures.
 6. The devicefor central feeding of a tank with fluid by utilization of the Coandaeffect, according to claim 3, wherein said one open end of said conduitpipe is substantially trumpet-shaped having a small diameter end and alarger diameter end, said small diameter end connected to said conduitpipe and said larger diameter end open to atmosphere and definingthereby a smooth and continuous region of transition from said largerdiameter end to said small diameter end.
 7. The device for centralfeeding of a tank with fluid by utilization of the Coanda effect,according to claim 3, further comprising an upstream immersed baffle,said upstream immersed baffle at least partially immersed below anexpected level of fluid when said fluid is in said tank and wherein aportion of said upstream immersed baffle projects above said expectedlevel of fluid, said upstream immersed baffle promoting separation offluids from expected particles floating on said fluid when said fluid isin said tank.
 8. The device for central feeding of a tank with fluid byutilization of the Coanda effect, according to claim 7, furthercomprising an inner immersed baffle running helically towards saidcentral portion of said tank, said inner immersed baffle arranged withinsaid upstream immersed baffle.
 9. The device for central feeding of atank with fluid by utilization of the Coanda effect, according to claim8, wherein said tank is an open top gravity discharge tank in whichfluid flows over an edge of at least one tank wall, said tank furthercomprising a tank cover positioned above said edge to permit fluid flowover said edge, and wherein said portion of said upstream immersedbaffle projecting above said expected level of fluid of said tank isattached to said tank cover.
 10. The device for central feeding of atank with fluid by utilization of the Coanda effect, according to claim2, further comprising an upstream immersed baffle, said upstreamimmersed baffle at least partially immersed below an expected level offluid when said fluid is in said tank and wherein a portion of saidupstream immersed baffle projects above said expected level of fluid,said upstream immersed baffle promoting separation of fluids fromexpected particles floating on said fluid when said fluid is in saidtank.
 11. The device for central feeding of a tank with fluid byutilization of the Coanda effect, according to claim 2, wherein saidtank further comprises:a tank cover sealed to an edge of a wall of saidtank; a plurality of slots each of said slots through said wall of saidtank each slot of said plurality of slots peripherally disposedproximate an edge of said wall to permit a pressure discharge of fluidinto a pressure discharge line.
 12. A method for central feeding of atank with fluid by utilization of the Coanda effect, said methodcomprising the steps of:producing a helical flow of fluid to becentrally fed; directing said helical flow of fluid through a verticalgravity outlet pipe, said vertical gravity outlet pipe having an axissubstantially vertically directed with respect to gravity with a firstend and a second end, said second end directed into a central portion ofsaid circular tank; and providing a fluid contacting surface of a bellshaped body, trumpet-shaped in that said bell shaped body is configuredsimilarly to a bell end of a trumpet, said bell shaped fluid contactingsurface in flow contact with said helical flow of fluid emerging fromsaid second end of said vertical gravity outlet pipe thereby utilizingthe Coanda effect and centrifugal forces for deflecting the fluid in adirection substantially radial relative to said vertical gravity outletpipe and guiding said helical flow of fluid emerging from said secondend of said vertical gravity outlet pipe into substantially a radialdirection relative to said vertical gravity outlet pipe and into saidtank to separate constituents entrained in said liquid and producingthereby a radially symmetrical distribution of said fluid into saidcircular tank to separate constituents entrained in said fluid.
 13. Themethod for central feeding of a tank with fluid by utilization of theCoanda effect, according to claim 12, further comprising introducing airinto vertical gravity outlet pipe of said helical flow.
 14. The methodfor central feeding of a tank with fluid by utilization of the Coandaeffect, according to claim 13, further comprising placing flocculatingagents into said air introduced into said vertical gravity outlet pipe.15. The method for central feeding of a tank with fluid by utilizationof the Coanda effect, according to claim 12, wherein said fluid is wastewater, further comprising the step of separating said constituentsentrained in said waste water thus clarifying said waste water.